never heard of marketbanker. adsense TOS prohibit place competitive contextual ads on the pages you place adsense, but you can place text link and affiliate links
I don't see a problem with using both Adsense and Marketbanker (now called Adbrite). You're right though - their filler ads are spammy, but you don't have to activate them. I use them on some of my sites and have had quite a few advertisers sign up for them. As long as you display them in a way that makes them not look like Adsense it shouldn't be a problem.